Sustainability is not simply an option to be chosen or rejected. By very simple, reasonable definitions, sustainability is inevitable. After all if an activity is unsustainable, it cannot continue indefinitely. Since sustainability is inevitable, achieving it is not the real challenge we face. Our challenge is to help in the transition to a society that offers the same or similar benefits to future generations as those we have enjoyed as we exploited a wide range of resources in an unsustainable manner. In a previous post (http://transitionmilwaukee.org/profiles/blogs/a-new-old-economics) I described a framework – protoeconomics – which helps me think about the details of this effort.
This transition to sustainability must address a large number of details. A particularly challenging detail is what the communities of the future will look like and how they will function. In this area, the political high ground is currently owned by urban advocates. Unfortunately as far as I have been able to figure out, the quality of their thought is little better than the thinking that brought us commuter suburbs, the bane urban advocates are intent on eliminating. They rightly observe that commuter suburbs are just about the worst form of human settlement (from the standpoint of sustainability) that has ever existed, and I agree with them on this point. Unfortunately they immediately conclude that huge cities are the only alternative.
If you view the question of what a sustainable community should look like from the perspective used by many energy analysts, you can get some important insights about what future communities should look like. Of the four (residential, commercial, industrial, and transportation) energy sectors, the first two are relatively easy to manage, so I will skip them for now. The industrial sector is harder, but not especially complex in a conceptual sense, so I will skip it as well.
The sector that is most challenging is transportation. Transportation can certainly be made more efficient and we are seeing progress on that. But an essential part of sustainable prosperity is reducing our reliance on powered transportation – using less of it. The simple answer to this requirement is walkable communities. To minimize reliance on transportation for society as a whole, communities must achieve a very high level of walkability.
In a sustainable community, most people will rarely use powered transportation themselves. People will walk to work, to school, to the store, to the doctor’s office. All normal, day-to-day activities for most people will be accomplished on foot or using human-powered transportation. I take this as a given, since energy and resource budgets will be small and will have to be allocated carefully.
A little simple math can help us determine the nominal size and some key characteristics of such a community. The results will not be precise – real life is profoundly complex and this math is not, However it can clarify a great deal about the community scale and layout required for prosperous, sustainable communities.
This arithmetic requires only three factors:
- the maximum distance a person will travel to work. A common number for this is approximately 2 miles (40 minutes walking, or 5-10 min on a bicycle)
- the area of farmland required to feed a person. Approximately ½ acre.
- the maximum distance a person will walk to get services. Approximately ½ mile (10 minutes at a good clip)
With these three parameters, you can figure out the basics of what a community should look like. Others may choose to use other values, which is a great idea. What is interesting about doing so with reasonable changes in these values has relatively modest impact on what the community looks like. I will run one example, but everyone should go ahead and do their own figuring to get a feel for how this stuff works.
The total area of a community depends more than anything else on the farmland required to support it. If the footprint is square and farthest corner of the farmland is 2 miles from the center of town (along a diagonal path from the center to any corner of the square footprint of the community), that means it is 1.4 miles from the community center to the flat edge of the square in all directions. In turn, this means that each side of the square is 2.8 miles. Therefore the total area of the town is just under 8 square miles, or approximately 5000 acres.
At a half acre per person, the maximum population of this community is about 10,000 people.
While it seems fine to walk diagonally through farmland to the most distant corners, I envision a populated area that is roughly square with a rectilinear layout of streets and walkways. This means that to keep the walking times down while walking on formal streets and walkways, the core would be at most 1/2 mile on a side (which would let you walk a quarter mile from a corner of the settled community core to the middle of one side, and another quarter mile from there to the center). At a population of 10,000 people this gets you a population density of 60 people per acre, which is dense but well within a normal range, and seems fine to me.
So using these assumptions, a sustainable community has a population of about 10,000 people in a moderately dense core with a band of farmland just under a mile wide surrounding this town center.
For an alternative view of what a sustainable community looks like, check out the Piscataquis Village Project. It is a great project and the mover and shaker behind it, Tracy Gayton, is a smart guy. He has done the same calculations and pushed his planned community toward a population of about 55,000 people living in a denser core. I like his ideas a lot. On the other hand, I can do similar calculations that suggest a community of 1000 people would work fine.
It could easily wind up that municipalities that host major transportation facilities (mostly on navigable waterways or at major rail junctions) will grow significantly larger than the 55,000 that Tracy envisions (or shrink down from their present proportions to a similar size). Such communities could take advantage of the higher availability of transportation to supplement the resources they use at relatively low cost in energy and resources. And of course communities with fewer than 1000 residents have proven sustainable throughout human history. It simply becomes more difficult to provide amenities in smaller communities.
Finally, the point of this post is not to suggest that we must immediately mandate the size and characteristics of all communities. Rather it is to try to inject a clearer notion of what sustainability means at the level of communities so that smart, caring people can be more effective in moving their own communities through transitions of the sort that Transition Towns are working on.